The main purpose of this research is to investigate the mechanism by which the formation of insoluble protein occurs during aging of human lens. Since calcium-sensitive fluorescent protein can be isolated from human lens insoluble protein by urea-treatment followed by dialysis and gel filtration, the behavior of reassembly of the urea-deaggregated lens insoluble protein will be studied by use of light scattering method and/or by laser photon correlation method to delineate the role of calcium ion plays in the aggregation process. The type of bonds involved in this aggregation will also be studied by measuring heat evolved as well as changes in circular dichroism of the lens protein during progress of the reaction. The amount of calcium ion incorporated into the aggregates formed, if any, will be determined by use of radioactive calcium. Physico-chemical characteristic of the fluorescent protein itself will also be investigated to obtain an insight into origin of the lens protein, and the characteristic will be compared with that of soluble crystallin proteins.